Key operated pulse generating device

ABSTRACT

A key operated electric pulse generator comprising a housing of non-magnetic material supporting depressible key at one end, a coil at the other end, and a body of magnetic material spaced from the coil. A permanent magnet is supported in the housing for movement between the magnetic body and the coil and is normally magnetically attracted to the magnetic body. A spring is interposed between the permanent magnet and the depressible key so that upon depression of the key the spring will yield a certain amount and then cause the magnet to abruptly release from the magnetic body and be impelled toward the coil to generate an electric signal.

"M [451 Sept. 19, 1972 KEY @PERATED PULSE GENERATING 3,132,268 5/1964Abel et al. ..310/15 DEVHQE 72 Inventor: Donald L. Troesh, Ontario,Calif. Pnmay ExammehD Dugga Att0rney-Fred N. Schwend [73] Assignee:Electromechanisms, lnc., Azusa,

Cahf- 57 ABSTRACT [22] Filed: June 1971 A key operated electric pulsegenerator comprising a 2 AWL 156,318 housing of non-magnetic materialsupporting depressible key at one end, a c011 at the other end, and abody of magnetic material spaced from the coil. A per- [52] US. Cl..310/14, 310/15 manem magnet is supported in the housing for move [51]Int. Cl. ..HOZk 35/00 mem between the magnetic body and the coil and is[58] Field (It Search ..310/12-15, 30 normally magnetically attracted tothe magnetic body A spring is interposed between the permanent magnet[56] References and and the depressible key so that upon depression ofthe UNITED STATES PATENTS key the spring will yield a certain amount andthen cause the magnet to abruptly release from the mag- 3,116,42812/1963 Blodgett et a1. ..3 10/ 15 netic body and be impelled toward thei to generate 3,065,366 11/1962 Sperser et al. ..310/15 an elecm-csignal 3,398,302 8/1968 Hamau et a1. ..310/14 3,153,735 10/1964 Branaganet a1 ..310/15 4 Claims, 3 Drawing Figures mmransmsmz 3,693,033

8 vours 5 mnusecouo Ill INVENTOR. DONALD L. T9055 BY XMXM BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention relates to keycontrolled electric pulse generating means.

2. Description of the Prior Art Heretofore, manually controlled electricpulse or signal transmitting devices for controlling electronic or thelike equipment generally comprised key operated contact opening orclosing devices. Such devices require a standby electrical circuit whichis made or broken by depression of a key. Also, the contacts of suchswitches tend to wear and to become oxidized or corroded after extensiveuse, resulting in unreliable switching operation. Further, such contactstend to bounce, which, when the contacts are in circuit with sensitiveelectronic equipment, gives rise to spurious and unwanted pulse signals.

Attempts have been made to overcome the above problems by providing akey operated permanent magnet which is moveable relative to a coil togenerate an electric signal as the magnetic field of the magnet cutsacross the windings of the coil. Although such pulse generating deviceswork generally satisfactorily, the size and wave form of the signalgenerated is dependent upon the speed and abruptness with which the keyis depressed. Thus, if the key is depressed too slowly, the resultingsignal may be of insufficient size or shape to adequately and reliablycontrol a signal responsive device.

SUMMARY OF THE INVENTION The present invention overcomes the aboveproblem by providing a permanent magnet which is coupled to adepressible key through a yieldable spring, and which by virtue of itsmagnetic attraction to a stationary magnetic body, forms the sole meansof maintaining itself spaced from an electric signal generating coil;Upon a predetermined depression of the key and consequent deformation ofthe spring, the magnet will abruptly release from the body and willadvance toward the coil at a maximum rate under the impetus of thespring to generate a sharply peaked signal pulse. It should be notedthat the size and shape of the wave form of such generated signal pulsewill be substantially consistent regardless of the speed or abruptnesswith which the key is depressed. Further, applicants constructionresults in a compact, self-contained pulse generating device which isadapted to be easily and readily mounted on a panel or the like. Theconstruction also results in a compact and economically manufactured andassembled device having relatively few moving parts, has an extremelylong operating life and may be safely used in explosive and otherdangerous environments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal sectionalview through a key operated pulse generating device embodying apreferred form of the present invention.

FIG. 2 is a transverse sectional view taken substantially along the line2-2 of FIG. 1.

FIG. 3 is a diagram of a wave form generated by the device ofFlGS. l and2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, thedevice comprises a hollow cylindrical housing 11 which is preferablymolded of plastic or other non-magnetic material. The housing is reducedin diameter at its righthand end and has a threaded section 12 adaptedto be mounted in an opening in a panel or other supporting member 13.The housing is secured to the panel by lock nuts 14 and 15 threaded onthe section 12.

A depressible key comprising a tubular keystem 16, also of plastic andhaving a key top 17 attached to its outer end, is slideable endwise in abore 18 formed in the housing. The inner end of the keystem 16 has aflange 20 normally abutting a shoulder 21 in the housing to limitmovement of the key.

A cylindrical cavity 22 is formed in the housing and communicates withthe bore 18 through an intermediate cylindrical cavity 23.

A cup shaped magnetic body comprising a disc 24 and a ring 25 fitted inthe cavity 22 is held in place against a shoulder 29 by a plastic ring26 and a coil bobbin 27, the latter being press fitted in the cavity 22.

The bobbin 27 comprises a tubular core 28 of magnetic material having alow magnetic retentivity and a high magnetic permeability, such as iscommercially available under the trade name Armco" iron. The core 28 issupported at opposites ends by flanges 30 and 31 of plastic or othernon-magnetic material. A coil 32 of wire is wound on the core 28 and itsends are electrically connected to terminal strips 33 and 34 forconnection to a suitable circuit (not shown) to be controlled bydepression of the key.

The disc 24 and ring 25 are formed of magnetic material, such as Armco"iron, having a low magnetic retentivity.

A plunger 35 of non-magnetic material, such as brass, is slideablymounted at one end thereof in the core 28 and at the opposite endthereof in the keystem 16 for endwise movement. An annular permanentmagnet 36 is mounted on the plunger and is held between annular discs 37and 38, which, in turn, are held in place on the plunger by two springclips 40 and 41 of non-magnetic material. The magnet 36 is formed of amagnetic material having a high degree of magnetic retentivity, such asis available under the trade name Alnico" and the discs 37 and 38 areformed of a magnetic material, such as Armco iron, having a low magneticretentivity and high permeability.

A compression spring 42 surrounds the plunger 35 and extends between theclip 41 and the flange 20 of the keystem l6.

Normally, when the key 17 is in its illustrated undepressed condition,the magnet 36 is attracted to the disc 24, thus lightly compressing thespring 42 to hold the key in its outer illustrated undepressed position.In such condition, the magnet 36 and discs 37 and 35 are maintainedwithin the ring 25 and the magnetic flux developed by the magnet extendsgenerally through the disc 38, disc 24, ring 25 and across the annularair gap 43 to the disc 37. The discs 37 and 38 tend to concentrate themagnetic flux therethrough and convey the same to and from the magnet36.

Upon depression of the key 17 through the latter portion of its fullstroke and consequent compression of the spring 42, the latter suddenlyovercomes the force of attraction of the magnet 36 and impels the magnetand the plunger 35 at a high rate of speed towards the coil 32.Accordingly, the magnetic flux path abruptly changes due to theincreasing air gap between the discs 24 and 38 and the receding of themagnet from within the ring 25. The flux path now abruptly expandsendwise toward the coil 32. At the same time, due to the rapid movementof the magnet 36 toward the coil, the lines of force of the magneticflux rapidly cut across the windings of the coil to develop an electricpulse or signal having a sharply peaked rise in voltage as depicted inFIG. 3. The core 28 tends to convey the lines of magnetic forcetherealong to distribute the same throughout the coil 32.

H6. 3 illustrates wave form developed from a device constructedaccording to FIG. 1 having a coil 32 formed of No. 46 copper wire with atotal resistance of 3,000 ohms.

Upon release of the key 17 from depressed position, the magnet willagain attract to the disc 24 and the ring 25 to return the parts totheir illustrated positions.

I claim:

1. A pulse generating device comprising a housing,

a coil in said housing adjacent one end of said houssaid coil having ahollow core,

a manually depressible key having a hollow keystem slidably supported bysaid housing adjacent the opposite end of said housing for endwisemovement;

a plunger in said housing slidably supported at one end thereof in saidcore and at the opposite end thereof in said keystem for endwisemovement,

spring means for yieldably transferring endwise movement between saidkeystem and said plunger,

a body of magnetic material fixed in said housing,

and

means forming a permanent magent fixed on said plunger,

said magnet being normally magnetically attracted to said body andspaced from said coil, and

said spring means being effective upon a predetermined depression ofsaid key to cause said magnet to release from said body and to approachsaid coil whereby to generate an electrical pulse in said coil.

2. A pulse generating device according to claim 1 comprising a member ofmagnetic material having rela tively low magnetic retentivity attachedto one end of said magnet and engagable with said body when said magnetis attracted to said body.

3..A pulse generating device according to claim 1 wherein said body iscup-shaped and has a radially inwardly extending end,

a pair of members of magnetic material having relatively low magneticretentivity attached to opposite ends of said magnet,

one of said members normally engaging the radially extending end of saidbody,

said magnet extending within said body when said magnet is attracted tosaid body whereby to form a substantially enclosing magnetic fluxpathfor said magnet, and

said magnet receding at least partially from within id 0d d rin ovementtoward said coil w iiere by ihe l i nes o magnetic force developed bysaid magnet will move across the windings of said coil. 4. A pulsegenerating device according to claim 3 comprising a core within saidcoil,

said core comprising a magnetic material having a relatively lowmagnetic retentivity.

1. A pulse generating device comprising a housing, a coil in saidhousing adjacent one end of said housing, said coil having a hollowcore, a manually depressible key having a hollow keystem slidablysupported by said housing adjacent the opposite end of said housing forendwise movement; a plunger in said housing slidably supported at oneend thereof in said core and at the opposite end thereof in said keystemfor endwise movement, spring means for yieldably transferring endwisemovement between said keystem and said plunger, a body of magneticmaterial fixed in said housing, and means forming a permanent magentfixed on said plunger, said magnet being normally magnetically attractedto said body and spaced from said coil, and said spring means beingeffective upon a predetermined depression of said key to cause saidmagnet to release from said body and to approach said coil whereby togenerate an electrical pulse in said coil.
 2. A pulse generating deviceaccording to claim 1 comprising a member of magnetic material havingrelatively low magnetic retentivity attached to one end of said magnetand engagable with said body when said magnet is attracted to said body.3. A pulse generating device according to claim 1 wherein said body iscup-shaped and has a radially inwardly extending end, a pair of membersof magnetic material having relatively low magnetic retentivity attachedto opposite ends of said magnet, one of said members normally engagingthe radially extending end of said body, said magnet extending withinsaid body when said magnet is attracted to said body whereby to form asubstantially enclosing magnetic fluxpath for said magnet, and saidmagnet receding at least partially from within said body during movementtoward said coil whereby the lines of magnetic force developed by saidmagnet will move across the windings of said coil.
 4. A pulse generatingdevice according to claim 3 comprising a core within said coil, saidcore comprising a magnetic material having a relatively low magneticretentivity.